netdev - Re: [PATCH] smsc911x: add fifo byteswap support

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Message-ID: <OF7ABB7A00.E22FC2BA-ON802575A2.005A9008-802575A5.002A2FDC@smsc.com>
Date:	Mon, 27 Apr 2009 08:40:49 +0100
From:	Steve.Glendinning@...c.com
To:	Magnus Damm <magnus.damm@...il.com>
Cc:	davem@...emloft.net, Ian.Saturley@...c.com, iwamatsu@...auri.org,
	lethal@...ux-sh.org, netdev@...r.kernel.org
Subject: Re: [PATCH] smsc911x: add fifo byteswap support

Hi Magnus,

Slight correction: the newer devices *can* handle this in hardware, there 
are registers to control this swapping but the driver doesn't currently 
use them.  If I see a suitably broken design with a newer device I'll 
submit a patch to add this.

Looks great otherwise, thanks for adding the "health warning" :-)

Regards,
--
Steve Glendinning
SMSC GmbH
m: +44 777 933 9124
e: steve.glendinning@...c.com



Magnus Damm <magnus.damm@...il.com> wrote on 24/04/2009 02:15:03:

> On Thu, Apr 23, 2009 at 12:21 AM,  <Steve.Glendinning@...c.com> wrote:
> > Magnus Damm <magnus.damm@...il.com> wrote on 22/04/2009 15:55:53:
> >> This patch adds fifo byteswap support to the smsc911x driver.
> 
> > Performance will be suboptimal with this software byteswapping,
> > so I think we should also add a comment to stress that this is
> > a "last resort" workaround for broken hardware.
> 
> Good idea. How about adding the following to the header file right
> before the SMSC911X_SWAP_FIFO definition:
> 
> /*
>  * SMSC911X_SWAP_FIFO:
>  * Enables software byte swap for fifo data. Should only be used as a
>  * "last resort" in the case of big endian mode on boards with 
incorrectly
>  * routed data bus to older devices such as LAN9118. Newer devices such 
as
>  * LAN9221 handle this in hardware.
>  */
> 
> Let me know if you want to improve the comment somehow, otherwise I'll
> just update the patch and repost a V2.
> 
> Cheers,
> 
> / magnus

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